Reading and writing text or binary files

You use PowerScript text file functions to read and write text in line mode or text mode, or to read and write binary files in stream mode:

NoteReading a file into a MultiLineEdit You can use stream mode to read an entire file into a MultiLineEdit, and then write it out after it has been modified.

Understanding the position pointer

When PowerBuilder opens a file, it assigns the file a unique integer and sets the position pointer for the file to the position you specify—the beginning, after the byte-order mark, if any, or end of the file. You use the integer to identify the file when you want to read the file, write to it, or close it. The position pointer defines where the next read or write will begin. PowerBuilder advances the pointer automatically after each read or write.

You can also set the position pointer with the FileSeek or FileSeek64 function.

File functions

These are the built-in PowerScript functions that manipulate files:

Table 3-1: PowerScript functions that manipulate files

Function

Datatype returned

Action

FileClose

Integer

Closes the specified file

FileDelete

Boolean

Deletes the specified file

FileEncoding

Encoding enumerated type

Returns the encoding used in the file

FileExists

Boolean

Determines whether the specified file exists

FileLength

Long

Obtains the length of a file with a file size of 2GB or less

FileLength64

LongLong

Obtains the length of a file of any size

FileOpen

Integer

Opens the specified file

FileRead

Integer

Reads from the specified file (deprecated)

FileReadEx

Long

Reads from the specified file

FileSeek

Long

Seeks to a position in a file with a file size of 2GB or less

FileSeek64

LongLong

Seeks to a position in a file of any size

FileWrite

Integer

Writes to the specified file (deprecated)

FileWriteEx

Long

Writes to the specified file

Encoding

The last argument in the FileOpen function lets you create an ANSI, UTF-8, UTF-16LE (Little Endian), or UTF16-BE (Big Endian) file.

The encoding argument, like all arguments of the FileOpen function except the file name, is optional. You need only specify it if you want to create a new text file with Unicode encoding. If the filename argument refers to a file that does not exist, the FileOpen function creates the file and sets the character encoding specified in the encoding argument.

By default, if the file does not exist and the encoding argument is not specified, PowerBuilder opens a file with ANSI encoding. This ensures compatibility with earlier versions of PowerBuilder.

The FileRead and FileWrite functions cannot read more than 32,766 bytes at a time. The FileReadEx and FileWriteEx functions can write an unlimited number of bytes at a time.